This invention relates generally to heat exchange, and more specifically, to methods and apparatus for exchanging heat within a gas turbine engine.
Gas turbine engines typically include a compressor for compressing air. The compressed air is mixed with a fuel and channeled to a combustor, wherein the fuel/air mixture is ignited within a combustion chamber to generate hot combustion gases. The combustion gases are channeled to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or power a load, such as an electrical generator.
At least some known gas turbine engines use heat exchangers to improve an efficiency of the gas turbine engine, for example, by increasing the temperature of air discharged from the compressor, or decreasing the temperature of air used to cool the turbine. At least some known gas turbine engines also use heat exchangers to decrease the temperature of gases exhaust from the turbine. Heat exchangers typically include a plurality of small diameter tubes that carry a first fluid therein and are suspended in a cross-flow of a second fluid. As the first fluid flows through the tubes and second fluid flows over the surface area of the tubes, the first and second fluids exchange heat. However, such heat exchangers can be complex and include a plurality of brazed joints, and may therefore be difficult to manufacture. In addition, the brazed joints or others areas of the tubes may crack under loading, thereby possibly mixing the first and second fluids.